Severing mechanism for bag making machines



June 24, 1941- T. SARGENT ETAL SEVERING MECHANISM FOR BAG MAKING MACHINES Filed Dec. 8, 1939 5 Sheets-Sheet 1 S v mm m T R//. R E m wf m M m m 5% Wm T5 B June 24, 1941. T. SARGENT EI'AL SEVERING MECHANISM FOR BAG MAKING MACHINES Filed Dec. 8, 1959 5 Sheets-Sheet 2 \NVENTORS:

Tom sHRCsENT' SHMUEL DLJERDEN HTTQRNEY June 24, 1941. T, SARGENT ETAL 2,247,069

SEVERING MECHANISM FOR BAG MAKING MACHINES Filed Dec. s, 19:59 s sheets-she'et 5 June 24, 1.94 T. SARGENT ET AL SEVERING MECHANISM FOR BAG MAKING MACHINES 5 Sheets-Sheet 4 Filed Dec. 8, 1959 INVENTOQS'. TOM sHRG-ENT SHMUEL DUERDEN FITTORNEY June 24, 1941. T. SARGENT ET AL SEVERING MECHANISM FOR BAG MAKING MACHINES Filed Dec. 8, 1939 5 Sheets-Sheet 5 W m u o m m EM WT MM u PM w AWE J m E mm Qw J w\ |i|m I I MllJl I VGSESZAZVC. E j @ww M QM M Q f v u W 1 w M A v WM mkR @QMMW FITT'ORNEI Patented June 24, 1941 SEVERING MECHANISM FOR BAG MAKING MACHINES Tom Sargent and Samuel Duerden, Whitehall,

Bristol,

England, assignors to Strachan &

Henshaw, Limited, Whitehall, Bristol, England, a company of Great Britain and Northern Ireland Application December 8, 1939, Serial No. 308,164 In Great Britain December 8, 1938 Claims.

This invention relates to severing mechanism for bag making machines for paper, Cellophane and like sheet material.

Various forms of severing mechanism are known for bag making machines, a number of which employ a rotary severing or beater arm which operates by knocking the two walls of the flat tube folded around the former plate upwards against serrated edges of the former plate and of a breaker plate in order to sever the bag blank. This method has the disadvantage of striking the paper at an angle to its direction of travel, which leads to choking or blocking of the flat tube adjacent the edges of the former plate.

It has previously been proposed to provide anperiodically the path of the web, said blades overlapping at the point of contact with the web whereby the path thereof is displaced and the web caused to change direction in passing each cutting edge so that one thickness of the web is severed against each cutter to produce an overlapping edge on the severed bag length.

With such an arrangement it is not necessary that the cutting blades, which actually have a serrated edge, should operate in conjunction with a former plate as the invention provides an arother form of severing mechanism (see British patent specification No. 25766/05) in which two oppositely rotating cutters disposed respectively on each side of the folded tube of paper co-operate respectively with oppositely slotted or serrated parts of the former plate to sever the two sides of the folded tube, the cutters rotating with a greater surface speed than the speed of, and at the moment of severance in the same direction as, the tube.

It has further previously been proposed (see British patent specification No. 1156/11) to use a roll or web of paper previously divided on one machine into a series of bag lengths by means of rows of perforations by a snatching action on a second machine.

The method proposed in specification No. 25766/05 (above referred to) would appear to oiier the advantage of efiecting the severing of the web substantially in the same direction as the direction of movement of the web but the cutting mechanism proposed involves the precise adjustment of the serrations on the rotary cutters relatively to the serrations in the former plate which is inconvenient or unsuitable where high operating speeds are involved.

The object of the present invention is to provide severing mechanism for a bag making machine in which the cutters act respectively on the two sides of the folded paper tube thereby avoiding the necessity for precise adjustment of thecutters and which, further, can be used for difierent lengths of bag without any adjustment other than the known adjustment of a change speed wheel.

According to the present invention web severing mechanism for bag making machines comprises means for traversing a web under tension, cutting blades arranged on opposite sides of said web in spaced relation and movable to int rs t rangement wherein the web is severed at two points along transverse parallel or approximately parallel lines, one line of severance being effected on one thickness of the web and the other line of severance on the other thickness of the web but spaced therefrom to provide overlapping ends to the bag length. The actual severing operation is eiiected whilst the web is between the tensioning means and is otherwise unsupported except for the contact with the cutting blade.

In order that the invention may be clearly understood reference is directed to the accompanying drawings wherein:

Figure 1 shows diagrammatically an assembly comprising a paper tube forming machine and from which is drawn a paper web in flat tube form, and a severing mechanism in accordance with the invention for severing such web into-bag lengths.

Figure 2 illustrates diagrammatically on a larger scale part of the severing mechanism shown in Figure 1 and showing the cutting blades of the severing mechanism in a position just prior to engagement with the paper web.

Figure 3 is a similar view to Figure 2 showing the cutting blades at a point where they are about to sever the web.

Figure 4 illustrates in longitudinal section a pair of associated cutting blades and the method of adjustably mounting them on rotating members.

Figure 5 is a section on the line 5-5 of Figure 4.

Figure 6 is a similar view to Figure 4 showing a further method of mounting the cutter blades, and i t Figure 7 is a section on the line 11 of Figure 6.

Figure 8 is a plan view illustrating a web as folded and delivered to the severing mechanism.

Fig. 9 is a sectional view taken on the line 99 of Fig. 4.

Referring now particularly to Figures 1, 2 and 3, the severing mechanism for a paper or like bag making machine made according to the present invention comprises a pair of draw rollers l and 2 including the known change speed mechanism (not shown) for accommodating the speed of a fiat tube A to the bag length for the time being, a pair of oppositely rotatingmembers 3 and 4 carrying cutting blades 5 and 6 respectively and operative on opposite sides of the flat tube A and a pair of snatch rollers I and 8. The treads of the snatch rollers and the operative edge of the cutters have a greater peripheral speed than the peripheral speed of the draw rolls so that at all times the peripheral speed of the cutters is substantially different from the surface speed of the tube A supplied by the draw rollers I and 2, irrespective of the size of the blank being severed.

The upper roller 1 of the pair of snatch rollers has a part of its periphery cut away as at 9 to.

provide a gripping surface It and this roller is set relatively to the cutters 5 and 6 whereby the snatch rollers grip the tube simultaneously with or immediately before the cutters act on the sides of the tube, whereby the snatch rollers make the tube taut simultaneously with or immediately prior to the action of the cutters.

The snatch rollers are so connected by gearing that the gripping surface H! of the upper snatch roll 1 works in unison with the rotating cutters 5 and 6 to place the web A under tension at the precise moment required. The usual draw rollers I and 2 supplying the tube to the cutters are of known construction driven by means of suitable change speed gearing to regulate the amount of tube necessary for different bag blank lengths. The web which is fed to the severing mechanism as previously stated is in the form of a tube which is supplied from a known form of paper tube forming machine such as illustrated diagrammatically at th right of Fig. 1 and comprising a paper supply roll H from which the paper passes through slitting mechanism indicated generally at 12, thence over a pasting roll l3 to folding mechanism indicated generally at M; at this point the paper tube A is formed and thereafter fed through the severing mechanism. The bag blanks produced are picked up by continuous band conveyors l5 and supplied to pasting and bottom folding mechanism indicated at IS. The slitting mechanism 12 produces a line of slits I! (see Fig. 8) which are formed coincident with the two lateral edges l8 of the tubular web A.

The operative edges of the cutting blades 5 and 6 are serrated, preferably of a fine gauge and the lower cutting blade 6 is displaced relatively to the top cutting blade 5v so that when contact is made upon rotation of the rollers with the tube to be severed the lower cutter is in advance of the upper cutter by an amount approximately equal to the amount it is required that one face of the severed bag blank shall overlap the other face see Fig. 8 where the dotted line l9 and the full line 20 indicate the amount of overlap and the lines of severance). The members and shafts supporting the said cutting blades are driven by means of suitable gearing so that they make one revolution for each bag blank to be severed.

The operation is as follows: The draw rolls l and 2 supply a predetermined length of .tube to the cutters which together with the snatch rollers 'l and 8 are rotating at a greater peripheral speed than the draw rollers. The cutters or their supporting members do not normally grip the tube, so that immediately before the severing operation the length of tube disposed between the cutter supports 3 and i and the snatch rollers 1 and 8 is slack because the snatch rollers at this time do not grip the tube and consequently there is nothing to pull the latter taut. In order to obtain a satisfactory severance the tube must be pulled taut simultaneously with or immediately prior to the serrated edges of the cutters 5 and 6 making contact with the tube.

The cutters are so arranged that they contact with the tube A at an acute angle, and as the rotation of the various members of the mechanism. is continued, the tube is pulled taut by the action of the snatch rollers I and 8, and at the same time the top cutter 5 presses the tube A downwards, while the bottom cutter 6, which is displaced in advance of the top cutter 5, presses the flattened tube A upwards. As the process is continued a point is reached where due to the cutters moving faster than the surface of the tube with which it is in contact, the said surface is pierced by the points of the serrated cutters, this causes a line of weakness along which tearing immediately occurs. To ensure that the line of weakness shall occur simultaneously in both the top and underneath walls of the flattened tube, we provide means whereby the angle of the cutting blades may be varied so that at the time when the tube is deflected upwards by the bottom cutter and downwards by the top cutter and the surface of the tube is pierced or about to be pierced by the points of the serrated cutters the angles made between the surface of the tube and the cutting blades shall be approximately equal to each other. By this means an equal amount of piercing of the top and bottom portions of the tube is obtained and ensures simultaneous tearing of the two surfaces of the tube. This adjustment of the cutting blades can be made when the machine is stopped, but in the preferred forms hereinafter to be described, means are provided for accomplishing this adjustment while the machine is in motion and it has been found that the desired result can be obtained by making this provision in one cutter, although it can be arranged for both cutters if desired.

Referring now to Figs. 4 and 5, 2| and 22 indicate the shafts carrying the top and bottom cutters 5 and 6 respectively, the said shafts being rotatably mounted in suitable bearings and connected together by gearing 23 to work in unison one with the other. Keyed to the top shaft 2| are supporting discs 24, 24 which support between them a cutter bar 25 to which the top cutter blade 5 is secured by screws, bolts, or other suitable means. The ends of the bar 25 are provided with curved spigots 26 which fit into curved recesses 21 cut in the supporting discs 24. Studs 28 serve for locking the bar 25 in any desired position. The spigots 26 and the recesses 2'! into which they fit are curved to a radius equal to the distance from the points of the cutter to the centre of the spigot, the arrangement being such thatthe angle of the cutter can be varied without altering the distance from the point of the cutter to the centre of its supporting shaft.

The lower cutter blade 6 is similarly mounted; that is to say, the spigot ends 26* of the lower cutter-carrying bar 25 are movable in corresponding recesses 2! in the lower bar-supporting discs 24 However, in order to provide for adjustment of the angle of the bar 25*, together with the cutter B, the shaft 22 is mounted for endwise movement as hereinafter more fully described, and the said bar is provided with two short quadrant gear segments 29, 29 the teeth of which are helical meshing respectively with two gears 39, 39, also provided with helical teeth, the arrangement being such that as the shaft 22 is moved endwise, the cutter supporting bar 25*, due to the action of the helical teeth, is caused to rotate about a virtual centre, which is the serrated edge of the cutter blade 6, thereby altering the angle of the cutter blade without altering the distance of the cutting edge from the centre of its supporting shaft 22. The discs 24 are slidably mounted on the shaft 22 and are retained in their correct angular position by feathers 3|.

So that the shaft may be readily moved endwise and after such movement be retained in the new position, one of the bearings of the said shaft is provided with a screw thread 32 on its outer surface working in a corresponding thread tapped into the supporting side frame 31 of the machine, the shaft 22 being held against longitudinal movement with relation to said bearing by a shoulder 22 formed on the shaft and abutting the bearing at one end thereof and a retaining washer 38 abutting against the opposite end of the bearing and secured by a bolt 39 extending into the end of the shaft. The said bearing is provided with means of rotating same under hand control such as the enlarged portion of the bearing 33, lock nut 34 being provided to secure the bearing against further movement in the frame when the desired angle of the cutting blade has been ascertained. This adjustment can readily be accomplished during operation by merely releasing the lock nut 34 and manually operating the enlarged portion 33 to rotate the bearing, it being understood that only a comparatively small rotary movement will be necessary.

Figures 6 and 7 show a construction of cutter mechanism substantially similar to that illustrated in Figs. 4 and and the same reference numerals are used for identical parts. In this construction, however, the supporting discs 24 and 2 .1 are connected by a housing 35 which forms, particularly for the lower cutter shaft 22 a protection for the helical gears 29 and 3!]. Further, the lower supporting bar 2'5 is of quadrantal cross section and the ends thereof are mounted in recesses 36 formed in the supporting discs 24*.

With the cutters correctly set and in combination with the tension exerted by the snatch rollers a leading portion of the tube is completely severed, experience has shown that with mechanism made in accordance with this invention only the surface of the tube adjacent to the cutter is weakened by contact with the points of the serrations, as immediately tearing commences the web tension of the tube is removed and the cutting blades pass over the underlying surface of the tube immediately above or below the cutting blades as the case may be, without piercing or cutting the said surface. The operation is facilitated by the provision of a series of short slits H in the web of the paper in the known manner, as previously described, the slits being arranged so that when the web of paper is formed into the flat tube they occur at the folded edges and at a point that will lie exactly between the top and bottom cutters during the severing operation. The length of the said slits being equal to the amount the points of the cutting blades overlap each other for the formation of the necessary stepped ends of the bag blank.

In bag making machines of the known type it is usual to form the tube from which the bag blanks are severed by folding a web of paper around a former plate, the leading edge of which is adapted to protrude into the draw rolls for the purpose of providing a cutting edge or ledger plate for the tube during the cutting operation. With the present invention, however, although a former plate may be employed for the tube formation and support, it is not an essential that it,

should protrude beyond the draw rolls to cooperate with the cutting blades. If desired, the former plate may be arranged that it does not support the tube beyond the draw rolls or if a modified form of tube formation is adapted the former plate may be dispensed with altogether, as with our invention the only support necessary to the tube during the severing operation being the snatch rolls, draw rolls and the cutting blades themselves when the tube is under tension.

Although the invention has been described as applied to the severing of blanks for the making of flat bags, it is applicable to the severing of gusseted tubes.

What we claim and desire to secure by Letters Patent is:

1. Mechanism for severing bag blanks from an interiorly unsupported tubular traveling web, comprising a pair of serrated blades extending transversely of the web and mounted for rotation at opposite sides of said web in spaced relation, the peripheral speed of said blades being faster than the surface speed of the web, said blades being adapted at each revolution thereof to contact the surface of said web at an acute angle and in the same direction of travel thereby to form transverse lines of perforations in opposite sides of the web, means operative simultaneously with the action of the blades to increase the tension on the web in the direction of travel thereby to sever the web along the lines of perforation, and means for varying the angle of the blades to each other and to the traveling web.

2. Mechanism for severing bag blanks from an interiorly unsupported tubular traveling web,

comprising a pair of shafts extending transversel ly of the web and mounted for rotation at opposite sides thereof, a pair of serrated blades carried by said shafts and adapted at each revolution of the shafts to contact the surface of said web at an acute angle thereby to form transverse lines of perforations in opposite sides of the web, means for varying the angle of said blades toward each other and toward the traveling Web, and means operative simultaneously with the contact of the blades with said web to increase the tension thereon in the direction of travel thereby to sever the web along the lines of perforation.

3. In a machine for severing bag blanks from a tubular traveling web, a pair of shafts mounted for rotation at opposite sides of the web and each having a pair of discs keyed thereto adjacent its opposite ends, each of said discs having a curved recess, a cutter bar having at its opposite ends curved spigots disposed in said recesses thereby to provide for angular adjustment of said bar, means for securing said spigots at any adjusted position, and a serrated blade secured to each of said cutter bars.

4. In a machine for severing bag blanks from a tubular traveling web, a pair of shafts mounted for rotation at opposite sides of the web and each having a pair of discs keyed thereto adjacent its opposite ends, each of said discs having a curved recess, a cutter bar having at its opposite ends in response to longitudinal movement of the shaft.

5. In a machine for severing bag blanks from a tubular traveling web, a pair of shafts mounted for rotation at opposite sides of the web and each having a pair of discs keyed thereto adjacent its opposite ends, each of said discs having a curved recess, a cutter bar having at its opposite ends curved spigots disposed in said recesses thereby to provide for angular adjustment of said bar,

means for securing said spigots at any adjusted position, a serrated blade secured to each of said cutter bars, one of said shafts having a bearing shiftable longitudinally with relation to the other shaft, means for maintaining said shiftable bearing in fixed longitudinal relation to its own shaft whereby the latter shaft is moved longitudinally with the bearing, and cooperating means carried by said longitudinally movable shaft and its cutter bar for imparting angular movement to the bar in response to the longitudinal movement of the shaft.

TOM SARGENT.

SAMUEL DUERDEN. 

